Media Gateway Control (MEGACO) protocol is RFC3015 protocol of the Internet Engineering Task Force (IETF).
FIG. 1 shows a system networking diagram for achieving MEGACO protocol. MEGACO protocol employs an idea of separating gateway, which divides a gateway processing signaling and media together into two parts: Media Gateway (MG) and Media Gateway Controller (MGC). MGC controls the operation of MG by MEGACO protocol in such a manner that MGC sends a command to be carried out to MG, and then MG carries it out and returns the result. MGC also processes event requests initiatively sent by MG. Logic relationship in MEGACO protocol is expressed by a connection model. Two basic components of the connection model are contexts and terminations. The context expresses connection and topography relationship between terminations.
Main commands between MGC and MG include SERVICECHANGE, ADD, MODIFY, SUBTRACT, NOTIFY and so on.
In a conventional method of authentication for Media Gateway, after MG registration is finished, MG is authenticated periodically by using a constant key. This has several disadvantages such that firstly if the same key is used for authentication for a long time, it is easy to be decoded by the third party. Secondly, in the method of periodical authentication, it is easy for the third party to make successful authentication between MGC and MG only by filtering the authentication message to real MG, and initiate a call by forging other MG messages. Thirdly, in the method, only MGC authenticates MG, therefore MG may be called by invalid MGC by forging messages.